Analyzers conventionally require that patient sample be brought into operative association, such as by aspiration and dispensing, with test reagents, which can be in a dried test element. This operative association usually is called a metering operation. If dispoable tips are used for the aspiration and dispensing, those tips are a further component that needs to be brought to the metering operation. The key component to the metering operation is aspirating and dispensing means, such as an automated pipette connected to means for evacuating and pressuring the pipette in alternating sequences.
One method of bringing the disposable tips, patient sample, and test elements "to " the pipette station is shown in U.S. Pat. No. 4,287,155, especially FIG. 3. In such an arrangement, the sample is transferred to open containers that are arranged on a rotating turntable (which may have four segements) in an arc. In another arc at a different radius on that turntable are placed disposable tips, so that the pipette first traverses to a position above the tips, lowers to pick up a tip, rises back to a traverse position, traverses to a position above the open sample containers, and lowers for aspiration. Thereafter the pipette traverses to another location to dispense sample onto a test element.
Such an arrangement has been very effective in analyzers that have been outstanding in the field of clinical chemistry. There are some aspects, however, which can be further improved. One of these is that the rotating turntable necessarily occupies much more volume than just that taken up by the arcuate arrangement of sample containers or of disposable tips. Therefore, the turntable is not very space-efficient nor does it allow for other turntables to be closely associated therewith. Another aspect for improvement is that each turntable necessarily limits its usefulness to there being an adequate number of disposable tips present for each sample container. If this is not the case, the analyzer sequence must be interrupted to provide extra tips, and such tips can be supplied only while an interrupt is in effect.
Still another area of improvement is to provide an analyzer that will allow STAT samples to be taken out of turn. Patient samples taken sequentially off a rotating turntable do not readily provide such a capability. Because of that, the prior turntable arrangement has induced operators to attempt to manually insert STAT samples in the turntable "close to" the position being aspirated. This not only creates a hazard to the operator but it can interfere with the automatic operation of the analyzer, particularly if the manual insertion fails in any respect.
Therefore, there has been a need prior to this invention to provide an analyzer with sample supply means that are more efficient in their use of space; accommodate additional, separately loadable sample supply means side-by-side; are independent of the supply of disposable tips; and/or allow for more random sampling of containers.
There have been some attempts at compacting trays of patient sample into linear arrays, so that a tray can be fed past a bar code reader to a metering station. For example, U.S. Pat. No. 4,727,033 teaches such an arrangement, using trays or racks 22, FIG. 2. However, in this arrangement, there is only one linear track (track 25) that is disposed to intersect the path of traverse of the metering pipette 32. As a result, the trays have to be mounted for movement into and out of the track 25 position. This in turn means that each tray is tied to, or in series with, the other trays, all in a track 20 that runs perpendicular to track 25. Thus, not only do all the trays have to be conveyed in a direction other than the operative one that intersects the metering pipette, but in addition there is no provision for removal of a tray from the sequence, until the tray reaches the end of track 20. There is no recognition in that patent that trays would benefit from being independently operable, such as would occur if each tray had its own separate track. That is, an individual tray containing a STAT sample cannot be taken out of order since the trays can be fed to track 25 only one at a time, in order. Furthermore, no provision is made to provide the pipette with disposable tips of any kind, let alone in a way that renders the supply of tips independent from the supply of patient sample.